In SVG, the color-interpolation property is used to control the colour
space in which SVG animations on properties like fill, stroke and
stop-color are performed. Should this apply to CSS Transitions and
Animations on properties that take colours too? It'd be good to have
the same interpolations available in both kinds of animation.
(Brian mentioned to me that people also want to be able to interpolate
in other colour spaces, like HSL or L*a*b too -- we could extend
color-interpolation with options for that.)